RRB Assistant Loco Pilot and Technician Model Paper 6 with solutions

Suppose each edge of the cube be x, on increasing 50% of each edge,
New edge = x + $\frac{1}{2}\mathit{x}=\frac{3}{2}\mathit{x}$
Original surface area of the cube = $6{\mathit{l}}^2=6{\mathit{x}}^2$
New surface area of the cube
= 6 ${\left(\frac{3\mathit{x}}{2}\right)}^2$
= $6\times \frac{9{\mathit{x}}^2}{4}$
= $\frac{27}{2}{\mathit{x}}^2$
Increase in surface area
= $\frac{27}{2}{\mathit{x}}^2-6{\mathit{x}}^2$
= $\frac{27{\mathit{x}}^2-12{\mathit{x}}^2}{2}$
= $\frac{15{\mathit{x}}^2}{2}$
∴ % increase = $\frac{\frac{15{\mathit{x}}^2}{2}}{6{\mathit{x}}^2}\times 100=125$